Putative spin liquid in the triangle-based iridate Ba$_3$IrTi$_2$O$_9$

TL;DR

This study investigates Ba$_3$IrTi$_2$O$_9$, revealing a spin-liquid-like state with persistent spin dynamics and no magnetic order down to very low temperatures, driven by frustrated geometry and strong spin-orbit coupling.

Contribution

It provides experimental evidence of a putative quantum spin liquid in a triangle-based iridate with strong spin-orbit coupling and complex magnetic interactions.

Findings

No long-range magnetic order down to 23 mK

Observation of T-linear and T-squared specific heat at low temperatures

Persistent spin dynamics indicating unconventional excitations

Abstract

We report on thermodynamic, magnetization, and muon spin relaxation measurements of the strong spin-orbit coupled iridate Ba$_3$IrTi$_2$O$_9$, which constitutes a new frustration motif made up a mixture of edge- and corner-sharing triangles. In spite of strong antiferromagnetic exchange interaction of the order of 100~K, we find no hint for long-range magnetic order down to 23 mK. The magnetic specific heat data unveil the $T$-linear and -squared dependences at low temperatures below 1~K. At the respective temperatures, the zero-field muon spin relaxation features a persistent spin dynamics, indicative of unconventional low-energy excitations. A comparison to the $4d$ isostructural compound Ba$_3$RuTi$_2$O$_9$ suggests that a concerted interplay of compass-like magnetic interactions and frustrated geometry promotes a dynamically fluctuating state in a triangle-based iridate.